1. Field of the Invention
The present invention relates to an internal printed antenna, especially to an internal printed antenna used for LTE700, GSM850/900, PCS, DCS, UMTS, LTE2300, and LTE2500 system operation without increasing antenna size.
2. Description of Related Art
Along with fast development of communication technology and popularity of electronic products, a plurality of communication protocols and technologies of wireless signal transmission have been developed. Wireless communication is more widely used by people and many portable electronics such as mobile phones and PDA can send and receive signals in different bands for more powerful communication capacities.
Generally, portable electronics are built-in with a dual-band or tri-band antenna so as to send and receive signals in different bands. However, such antenna operates only in two or three separate bands, without ranging bands commonly used. Refer to U.S. Pat. No. 6,727,854, a planar inverted-F antenna is revealed. The operating frequency band of the antenna is within bands of the GSM900 system and the DCS system.
Moreover, refer to Taiwanese Patent Pub. App. No. 1254493, a dual-band inverted-F antenna is disclosed. By two radiating elements having a T-shaped radiating metal part and an adjustment metal sheet, bandwidth, impedance matching and gain of the antenna are adjusted to achieve dual-frequency or multiple frequency operation. However, the frequency of bands available now is lower. Such design not only increases the antenna size that occupies space and doesn't meet requirements of light weight and compact design. Moreover, the resonance of the resonant multi-pathway resonance makes the antenna structure become more complicated. The manufacturing processes are complex and the cost is increased.